BACKGROUND: Firefighters partake in and are exposed to a range of potentially traumatic events throughout their careers and the impact of such critical events could last a life time. Therefore, capturing such lifetime exposures is necessary for supporting firefighter health. OBJECTIVE: To estimate the prevalence of critical incidents in firefighters across Canada and determine whether the number of critical events varied based on age, gender, years of service; and to integrate our prevalence estimates using meta-analysis with previous studies to provide a pooled estimate. METHODS: We recruited 464 firefighters. Firefighters were asked to complete a self-report Critical Incident Inventory (CII) survey that included questions on exposure to critical events throughout their firefighting careers. Individual CII items were summarized as percentages, number of exposures, the total number and percentages of exposures to each of the six CII sub-scales. We also performed a multivariate enter regression analysis with the CII total score as dependant variable, and age, gender, years of service as independent variables, to estimate if the number of critical incidents among firefighters varied based on age, gender and years of service. RESULTS: Among the 390 full-time firefighters, 376 (96.4%) indicated exposure to some type of critical incident. More specifically, 351 (90%) reported a “respond to incident involving one or two deaths”, and 314 (81%) reported a “respond to incident involving multiple serious injuries”. Age, gender and years of service accounted for only 37.4% of the variance in the number of critical incidents among firefighters. In addition, our pooled estimate results of previous similar studies indicated an overall prevalence estimate of critical incident exposures was 93.40% (4 studies, 1725 of 1877 firefighters, 95% CI: 82.26 –99.30). CONCLUSIONS: Nearly all (96.4%) firefighters were exposed to some form of critical event over the span of their entire firefighting careers. Age, gender and years of service accounted for one-third of the variance in the number of critical incident exposures among firefighters.